A silver halide color photosensitive material has so far been well-known to generate undesirable color stain between silver halide emulsion layers different in color sensitivity. As a means to inhibit the color stain, there is proposed, e.g., the method of using hydroquinone compounds in U.S. Pat. No. 4,732,845. Although hydroquinone compounds have some effect upon inhibition of color stain, they have drawbacks, e.g., of generating colored matter after performing their function as color stain inhibitor and causing undesirable changes in photographic properties during preparation and storage of sensitive materials.
On the other hand, EP-A2-0338785, JP-A-03-164735 (the term "JP-A" as used herein means an "unexamined published Japanese patent application") and JP-A-05-232651 disclose the use of nondiffusible hydrazine compounds as color fog inhibitors. Although the nondiffusible hydrazine compounds disclosed therein include some phosphorylhydrazine compounds, those phosphorylhydrazine compounds have little effects on the inhibition of color fog. Therefore, introduction of further improvements in them has been requested. Further, JP-A-60-140340, JP-A-63-223744, JP-A-63-286840, JP-A-63-234244, JP-A-63-306438, JP-A-05-165134, JP-A-05-197091, JP-A-05-142688, JP-A-02-1834 and so on use hydrazine compounds as nucleation agent in photographic systems, and some phosphorylhydrazine compounds are presented therein. However, those compounds react directly with silver halides to cause alterations in photosensitivity. Accordingly, they cannot answer the purposes of the present invention. As for the use in systems other than the photographic system, U.S. Pat. No. 4,203,932 demonstrates that phosphorylhydrazines are effective insecticides. However, none of the above-cited references have any descriptions of the compounds having the structure according to the present invention, or the structure in which hydrazine moieties are attached directly to a phosphorus atom. Therefore, the compounds of the present invention have structural novelty, and it was unexpected that these compounds could solve the aforesaid problems in the photographic system.